How is it listed on these exchanges before the mainnet launch? Is this like a speculated grey market trading price, at which these orders would be executed after mainnet launch?
These are futures, as was the case with many other coins.
Miners will receive their coins after the launch of the mainnet. The new project roadmap says that the launch of the mainnet is expected in July 2023. The price of the coin on the exchanges after the launch of the mainnet will fall.